Luggage, backpacks, and other apparatus for carrying gear such as clothing, books, and personal items are widely used for many different applications. Luggage is, of course, indispensable for travelers, and may be quite large and bulky. Backpacks are used not only for outdoor activities such as camping and hiking, but also, for example, by students to carry books and the like, and by others for carrying personal items. Modern materials and construction methods have increased the strength and capacity of such carriers, allowing the user to significantly increase the loaded weight of the carrier. Moreover, travelers often elect to carry their luggage onto the aircraft or other transportation, rather than checking their bags. Although carry-on luggage may significantly reduce the time required at the airport, this may require the traveler to carry a heavy bag a relatively long distance, e.g., through the airport concourse. As the population ages, however, many travelers may be unable and/or unwilling to carry a heavy container over a long distance. Similarly, improved backpacks have enabled students to carry more books and other items to and from school. Often, however, the student must carry the heavy backpack a significant distance.
Wheeled carriers have been developed that address some of the difficulties associated with transporting relatively heavy loads over relatively long distances. Typically, a frame for the carrier includes two or more fixed wheels mounted on the bottom of the carrier, and a retractable handle or a strap may be provided at one end, allowing the carrier to be pulled on the wheels by the user. Such wheeled systems have been very helpful at alleviating the difficulties discussed above, and are used widely.
Fixed wheel systems, however, have several disadvantages. In backpacks, for example, the fixed wheels can interfere with or generate discomfort when carrying the backpack and/or can result in soiling the user's clothes when the backpack is carried on the user's back. Also, fixed wheels are susceptible to being damaged during handling—for example, by baggage handling equipment when such luggage is checked through on a flight. Fixed wheel systems may also get in the way during storage and are aesthetically unappealing. To alleviate these problems, some fixed wheel systems use very small wheels. Small wheels, however, can be very difficult on which to pull heavy weights, particularly on a textured surface, and may be virtually useless on rough surfaces.
Retractable wheel systems have been proposed, but prior art retractable wheel systems are relatively complicated, expensive to produce, and prone to damage or malfunction. In particular, many prior art retractable wheel systems utilize a plurality of levers to extend and lock and/or retract the wheels. Such lever systems are susceptible to misalignment, loss of pivot pins, bending of the lever arms, and the like. Lever systems also typically lock rigidly into place, which can cause damage during use—for example, when the carrier is pulled over uneven terrain. They may also be difficult to extend and retract and/or may retract unexpectedly during use. The systems also typically require a relatively large clearance space to accommodate the lever arms, reducing the available volume in the carrier.
There remains a need, therefore, for a retractable wheel system for carriers, which is simple, reliable, inexpensive to produce, and easy to use.